The invention herein is broadly concerned with endoscopic procedures, and more particularly with arthroscopic surgery.
Arthroscopic surgery is a minimally invasive therapeutic and/or diagnostic procedure, during which small sized visualization and surgical tools are introduced into a joint cavity (most commonly a knee) through very small incisions. Typically, at least three incisions are employed for a therapeutic procedure and at least two for a diagnostic procedure. During the surgery, irrigation of the joint is necessary for the following reasons:
(1) Inflation of the joint is desirable for better visualization and access achieved by an increased joint or tissue separation. This is accomplished by application of pressure through the medium of the irrigation fluid.
(2) Flow of the irrigation fluid through the joint keeps the field of view clear and eliminates any loose debris.
(3) The fluid keeps the joint lubricated and replaces lost body fluids.
There are thus two independent factors at work here, the pressure and the flow rate of the irrigation fluid. The function and need for independent control of these two factors can be illustrated by the following situations:
(a) There are times during the surgical procedure when one needs to view and reach the far or posterior end of the joint. The joint separation needs to be increased without any need for an increased flow. A higher pressure in the joint will achieve this.
(b) If there is debris or bleeding in the cavity, a quick flush of fluid is needed to clear the field of view. Such conditions require a higher fluid flow rate without a higher pressure, assuming the joint separation is adequate.
(c) When an accessory instrument, like a shaver with wall suction, is used, a higher fluid inflow is required to keep up with the increased demand and prevent the joint from collapsing. A higher flow rate but the same set pressure is needed here.
Currently, the typical solution is to use saline bags hung above the patient's level. The bags are raised to obtain more pressure and the flow rate is controlled by using variable clamps on the tubing leading to and away from the patient. The control for the two operations is manual and decided upon by the surgeon.
An automated pressure regulating system, manufactured by F. M. Wiest KG of Germany, utilizes a pump with pressure measured in the joint and a feedback used to control the pump speed (flow rate). If the pressure is low, the pump automatically speeds up to compensate, and if the pressure is high, the pump slows down. In this system, the flow is dependent on the desired pressure and cannot be controlled independently.
U.S. Pat. No. 4,261,360, issued Apr. 14, 1981 to Jose A. Perez, discloses a two pump irrigation system for transurethral irrigation to maintain a constant volume of fluid in a bladder. If there is no bleeding, the inflow and outflow rates will be the same and the bladder, if not disturbed, will maintain a constant volume and hence constant pressure. It will also do so if there is bleeding into the bladder. However, if there is an increase in bladder pressure due to a compression of the bladder (no significant change in volume), the Perez system will neither detect it nor take any corrective action. Also, if there is any leakage from the bladder, the Perez system will not compensate for that loss. This could result in a decreased bladder fluid volume (distension) and pressure. To obtain a higher distension/pressure in the system, a higher flow rate would need to be selected manually.